Different antecedents of packaging machines exist on the market, which make containers continuously from one or more sheets of weldable thermoplastic material, and these containers are filled with the product to be packaged and subsequently sealed conveniently.
These packaging machines usually comprise welding devices formed of heated soldering irons attached to actuating clamps that carry out alternate opening and closing movements. When the clamps are closed, the heated soldering irons act on the superimposed layers of material to be welded, causing them to be welded together.
Static welding devices, which are unable to move in the direction in which the layers of material to be welded advance, require the sheets or layers of material making up the container to move intermittently, carrying out the welding when the progress of the layers of material to be welded stops. Obviously, this type of welding device prevents really continuous operating of the packaging machine.
Welding devices also exist that have heated soldering irons attached to opening and closing clamps, in the same way as the previous ones, but which can be displaced longitudinally in a different way, accompanying the layers of material to be joined as they are welded together, and returning to the original open position to begin a new welding cycle.
These welding devices, which are able to move differently in a longitudinal direction, enable continuous work to take place, but have limited production capacity, precisely because of the complexity of the necessary mechanisms causing the rapid forward and backward movement, and the inertia caused by this movement.
It should be mentioned that these welding devices, with heated clamps, are used both for welding the perimeter of the container, horizontally and vertically, and for joining other layers of material, for example surface areas or lateral sides of the containers, with continuous closing elements, by means of complementary seals that make the successive opening and closing of the container possible once it is open.
Consequently, the aforementioned welding devices present the inconvenience of limiting the production capacity of packaging machines, and an additional problem consists of the possible existence of waste or particles from material to be packaged, in areas in which welding takes place, preventing the heated clamps from providing a tight seal on the container, especially in the case of liquids. Manufacturers of packaging machines are perfectly aware of this problem, especially when they package liquid, doughy or granulated products.
In addition to the aforementioned problem, it should be highlighted that the most problematic welding to be conducted for containers is when it is oriented longitudinally, in the direction of movement of the containers, as this welding has a longer length than vertical welding, which can be made more easily and in less time due to the shorter length in the direction of movement of the containers.
Consequently, the technical problem approached involves a longitudinal continuous welding device for packaging machines that enables longitudinal welding to be carried out continuously, without the need for the layers of material due to be welded to trace intermittent stop-start movements, and without the welding device needing to trace longitudinal forward and backward movements.
Another objective of the invention is to enable the longitudinal continuous welding device to be suitable for the layers of material to be welded, whether these are the opposite sides of a container itself, or the sides of complementary means of closing the container, a zip-style seal for example, and regardless of whether there are remains of the material to be packaged between the layers of material to weld.